1. Field of the Invention
The invention relates to communication systems, and more particularly to a scheme for performing secure communications in a wireless local area network.
2. Description of the Related Art
A wireless local area network (WLAN) is a flexible data communications system that can either replace or extend a wired LAN to provide added functionality. Using radio frequency (RF) technology, WLANs transmit and receive data over the air, through walls, ceilings and even cement structures, without wired cabling. A WLAN provides all the features and benefits of traditional LAN technologies like Ethernet and Token Ring, but without the limitations of being tethered to a cable. This provides greatly increased freedom and flexibility.
The most common WLANs currently are those conforming to the IEEE 802.11 standard family. Not only are they increasingly deployed in private enterprise applications, but also in public applications such as airports and coffee shops. Since WLAN was designed as a wireless extension of the Ethernet for indoor use, it has adopted a simple protocol known as wired equivalent privacy (WEP) for authentication and encryption. According to WEP, every WLAN station and every access point in a Basic Service Set share a common, static key, called a WEP key. It has either 40 bits (standard) or 128 bits (optional). The authentication process is either an open authentication based on some advanced authentication method or a challenge and response authentication based on the WEP key. The encryption algorithm is RC4 with the key sequence generated by the WEP key and a random vector. However, the security flaws of WEP have been highly publicized, mainly due to the implementation flaw of the key scheduling algorithm in the RC4 encryption algorithm and the use of a static WEP key shared by every entity.
To address the security flaws related to WEP, the IEEE 802.1x standard has been introduced and the IEEE 802.11i standard is currently under development. Using the IEEE 802.1x standard along with various EAPs, or Extensible Authentication Protocols, WLAN authentication can be managed from a centralized server such as a RADIUS server, by means of session-specific keys for encryption purposes. Security flaws in the RC4 algorithm in WEP can be alleviated to some extent if the session-specific key is changed frequently. According to the IEEE 802.11i standard draft, the Advanced Encryption Standard (AES) will become the ultimate encryption algorithm to protect over-the-air traffic.
The cryptographic functions, however, are some of the most CPU-hungry algorithms to conventional security designs targeted at software. It would be desirable to off-load the cryptographic functions from the CPU. Furthermore, the load generated by security operations often consumes most of the system bus bandwidth so conventional WLAN equipment poses performance problems. Therefore, what is needed is a scheme for performing secure communications in a WLAN, achieving overall system cost effectiveness